1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef APR_GLOBAL_MUTEX_H
18#define APR_GLOBAL_MUTEX_H
19
20/**
21 * @file apr_global_mutex.h
22 * @brief APR Global Locking Routines
23 */
24
25#include "apr.h"
26#include "apr_proc_mutex.h"    /* only for apr_lockmech_e */
27#include "apr_pools.h"
28#include "apr_errno.h"
29#if APR_PROC_MUTEX_IS_GLOBAL
30#include "apr_proc_mutex.h"
31#endif
32#include "apr_time.h"
33
34#ifdef __cplusplus
35extern "C" {
36#endif /* __cplusplus */
37
38/**
39 * @defgroup APR_GlobalMutex Global Locking Routines
40 * @ingroup APR
41 * @{
42 */
43
44#if !APR_PROC_MUTEX_IS_GLOBAL || defined(DOXYGEN)
45
46/** Opaque global mutex structure. */
47typedef struct apr_global_mutex_t apr_global_mutex_t;
48
49/*   Function definitions */
50
51/**
52 * Create and initialize a mutex that can be used to synchronize both
53 * processes and threads. Note: There is considerable overhead in using
54 * this API if only cross-process or cross-thread mutual exclusion is
55 * required. See apr_proc_mutex.h and apr_thread_mutex.h for more
56 * specialized lock routines.
57 * @param mutex the memory address where the newly created mutex will be
58 *        stored.
59 * @param fname A file name to use if the lock mechanism requires one.  This
60 *        argument should always be provided.  The lock code itself will
61 *        determine if it should be used.
62 * @param mech The mechanism to use for the interprocess lock, if any; one of
63 * <PRE>
64 *            APR_LOCK_FCNTL
65 *            APR_LOCK_FLOCK
66 *            APR_LOCK_SYSVSEM
67 *            APR_LOCK_POSIXSEM
68 *            APR_LOCK_PROC_PTHREAD
69 *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
70 *            APR_LOCK_DEFAULT_TIMED pick the default timed mechanism
71 * </PRE>
72 * @param pool the pool from which to allocate the mutex.
73 * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
74 *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
75 */
76APR_DECLARE(apr_status_t) apr_global_mutex_create(apr_global_mutex_t **mutex,
77                                                  const char *fname,
78                                                  apr_lockmech_e mech,
79                                                  apr_pool_t *pool);
80
81/**
82 * Re-open a mutex in a child process.
83 * @param mutex The newly re-opened mutex structure.
84 * @param fname A file name to use if the mutex mechanism requires one.  This
85 *              argument should always be provided.  The mutex code itself will
86 *              determine if it should be used.  This filename should be the
87 *              same one that was passed to apr_global_mutex_create().
88 * @param pool The pool to operate on.
89 * @remark This function must be called to maintain portability, even
90 *         if the underlying lock mechanism does not require it.
91 */
92APR_DECLARE(apr_status_t) apr_global_mutex_child_init(
93                              apr_global_mutex_t **mutex,
94                              const char *fname,
95                              apr_pool_t *pool);
96
97/**
98 * Acquire the lock for the given mutex. If the mutex is already locked,
99 * the current thread will be put to sleep until the lock becomes available.
100 * @param mutex the mutex on which to acquire the lock.
101 */
102APR_DECLARE(apr_status_t) apr_global_mutex_lock(apr_global_mutex_t *mutex);
103
104/**
105 * Attempt to acquire the lock for the given mutex. If the mutex has already
106 * been acquired, the call returns immediately with APR_EBUSY. Note: it
107 * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
108 * if the return value was APR_EBUSY, for portability reasons.
109 * @param mutex the mutex on which to attempt the lock acquiring.
110 */
111APR_DECLARE(apr_status_t) apr_global_mutex_trylock(apr_global_mutex_t *mutex);
112
113/**
114 * Attempt to acquire the lock for the given mutex until timeout expires.
115 * If the acquisition time outs, the call returns with APR_TIMEUP.
116 * @param mutex the mutex on which to attempt the lock acquiring.
117 * @param timeout the relative timeout (microseconds).
118 * @note A negative or nul timeout means immediate attempt, returning
119 *       APR_TIMEUP without blocking if it the lock is already acquired.
120 */
121APR_DECLARE(apr_status_t) apr_global_mutex_timedlock(apr_global_mutex_t *mutex,
122                                                 apr_interval_time_t timeout);
123
124/**
125 * Release the lock for the given mutex.
126 * @param mutex the mutex from which to release the lock.
127 */
128APR_DECLARE(apr_status_t) apr_global_mutex_unlock(apr_global_mutex_t *mutex);
129
130/**
131 * Destroy the mutex and free the memory associated with the lock.
132 * @param mutex the mutex to destroy.
133 */
134APR_DECLARE(apr_status_t) apr_global_mutex_destroy(apr_global_mutex_t *mutex);
135
136/**
137 * Return the name of the lockfile for the mutex, or NULL
138 * if the mutex doesn't use a lock file
139 */
140APR_DECLARE(const char *) apr_global_mutex_lockfile(apr_global_mutex_t *mutex);
141
142/**
143 * Get the mechanism of the mutex, as it relates to the actual method
144 * used for the underlying apr_proc_mutex_t.
145 * @param mutex the mutex to get the mechanism from.
146 */
147APR_DECLARE(apr_lockmech_e) apr_global_mutex_mech(apr_global_mutex_t *mutex);
148
149/**
150 * Get the mechanism's name of the mutex, as it relates to the actual method
151 * used for the underlying apr_proc_mutex_t.
152 * @param mutex the mutex to get the mechanism's name from.
153 */
154APR_DECLARE(const char *) apr_global_mutex_name(apr_global_mutex_t *mutex);
155
156/**
157 * Set mutex permissions.
158 */
159APR_PERMS_SET_IMPLEMENT(global_mutex);
160
161/**
162 * Get the pool used by this global_mutex.
163 * @return apr_pool_t the pool
164 */
165APR_POOL_DECLARE_ACCESSOR(global_mutex);
166
167#else /* APR_PROC_MUTEX_IS_GLOBAL */
168
169/* Some platforms [e.g. Win32] have cross process locks that are truly
170 * global locks, since there isn't the concept of cross-process locks.
171 * Define these platforms in terms of an apr_proc_mutex_t.
172 */
173
174#define apr_global_mutex_t          apr_proc_mutex_t
175#define apr_global_mutex_create     apr_proc_mutex_create
176#define apr_global_mutex_child_init apr_proc_mutex_child_init
177#define apr_global_mutex_lock       apr_proc_mutex_lock
178#define apr_global_mutex_trylock    apr_proc_mutex_trylock
179#define apr_global_mutex_unlock     apr_proc_mutex_unlock
180#define apr_global_mutex_destroy    apr_proc_mutex_destroy
181#define apr_global_mutex_lockfile   apr_proc_mutex_lockfile
182#define apr_global_mutex_mech       apr_proc_mutex_mech
183#define apr_global_mutex_name       apr_proc_mutex_name
184#define apr_global_mutex_perms_set  apr_proc_mutex_perms_set
185#define apr_global_mutex_pool_get   apr_proc_mutex_pool_get
186
187#endif
188
189/** @} */
190
191#ifdef __cplusplus
192}
193#endif
194
195#endif  /* ndef APR_GLOBAL_MUTEX_H */
196